The present invention relates to a battery module, and particularly to an improved structure for connecting a plurality of such battery modules arranged adjacent each other to constitute a battery pack.
A known battery pack is constructed with a plurality of prismatic battery modules coupled adjacent each other and connected in series. End plates are arranged on the opposite ends in the direction of arrangement of the battery modules, and the battery modules are coupled together by binding these end plates with restricting bands. In such battery pack, a large number of projections are formed dispersed on both sides of each battery module so that coolant passages are formed between the plurality of battery modules when they are abutted adjacent each other. Moreover, locating protrusions and corresponding indentations are provided on both side faces of each battery module, that couple each other when the plurality of battery modules are aligned adjacent, thereby determining relative positions of neighboring battery modules.
The battery pack of this type is herein described with reference to FIGS. 7A, 7B, and 8. One battery module 31 comprises an integral battery case 32, that is formed by mutually coupling a plurality of prismatic cell cases 33 having short lateral walls and long lateral walls such that each of the short lateral walls of these cell cases is common to two adjacent cell cases as partition walls 34. Each cell case 33 accommodates therein elements for electromotive force in a sealed condition. A positive electrode connecting terminal 35 and a negative electrode connecting terminal 36 are respectively arranged at opposite ends in the lengthwise direction of the integral battery case 32. On both side faces of the battery module 31, ribs 37 are formed at positions corresponding to the partition walls of each two neighboring cell cases, so that, when two battery modules 31 are arranged adjacent each other, they abut each other and together form coolant passages 40 between the battery modules. Further, a large number of projections 38 are protruded in a matrix fashion between the ribs 37. Both of the ribs 37 and the projections 38 have the height.
Moreover, as shown in FIG. 8, locating protrusions 41 and corresponding indentations 42 for receiving the locating protrusions when two battery modules are arranged side by side, for determining relative positions of neighboring battery modules 31 in a direction orthogonal to the direction of arrangement of the battery modules, are provided at opposite ends on both side faces of the battery module 31. More specifically, at one end of the battery module, a protrusion 41 is protruded on one side while an indentation 42 is formed on the other side, and at the other end of the battery module, an indentation 42 is formed on one side while a protrusion 41 is protruded on the other side.
However, there was the following problem in the above connecting structure of the battery pack. That is, there are inevitably variations in the width W (FIG. 7A) of each battery module 31, and if the variation occurs on the plus side, the integral battery cases 32 of the battery modules 31 will be subject to a great load of compression, because the battery pack is constructed with the plurality of battery modules 31 arranged adjacent each other and bound tightly together. In addition, each integral battery case 32 receives a load from the inside of the battery module, that is generated by rises in the internal pressure of the battery module upon expansion of electrode plate group during charging and discharging or upon generation of gas. As a result, the end plates are deformed because of an excessive load, whereupon the battery modules can no longer be tied together.
Furthermore, since the locating protrusions 41 and indentations 42 are arranged such as shown in FIG. 8, it is possible to connect two battery modules 31 side by side, the protrusions 41 respectively fitting into corresponding indentations 42 as shown in FIG. 9, in a state that the connecting terminals 35, 35 and 36, 36 of positive polarity and of negative polarity are aligned adjacent each other. Therefore, there is the risk that the battery modules 31 can be connected by mistake in such a wrong arrangement.
In view of these problems of the prior art, it is an object of the present invention to provide an improved structure for connecting battery modules to construct a battery pack, wherein the load exerted to each of the battery modules that are bound together can be reduced, whereby deformation of end plates can be prevented, and there is no risk of connecting electrode connecting terminals of the same polarity of two neighboring battery modules by mistake.
To achieve the above object, a battery module according to the present invention comprises:
a plurality of prismatic cell cases having short lateral walls and long lateral walls coupled together such that each of the short lateral walls of these cell cases is common to two adjacent cell cases as partitions, thereby constituting an integral battery case, and each of the cell cases respectively accommodating therein elements for electromotive force; and
a plurality of projections formed dispersedly on both side faces of the battery module for forming coolant passages between two battery modules when butted with corresponding plurality of projections formed on both sides of an adjacent battery module, wherein
part of the projections positioned opposite the partitions in the integral battery case have a height smaller than the other projections.
According to the battery module of the present invention, when a plurality of battery modules are arranged side by side and bound together with a pair of end plates arranged at their opposite ends, even when there is variation on the plus side in the width of the battery modules, it can reliably be prevented that the portions of the battery module corresponding to the partitions of the cells are subject to excessive compression load exerted on the integral battery case in addition to the load generated within the battery module. Accordingly, the end plates can be prevented from being deformed by an excessive binding load.
Moreover, a battery module according to the present invention comprises:
a prismatic battery case;
a connecting terminal of positive polarity and a connecting terminal of negative polarity arranged respectively at lengthwise opposite ends of the battery case; and
a plurality of protrusions and a plurality of indentations formed on both side faces of the battery case at positions near the lengthwise opposite ends of the battery case symmetrical with respect to a centerline in the lengthwise direction of the battery case, wherein the protrusions are in pairs formed opposite each other to protrude from opposite side faces of the battery case, and the indentations are in pairs formed opposite each other on the opposite side faces of the battery case.
With this arrangement, when neighboring battery modules are arranged wrongly such that their connecting terminals of the same polarity are aligned in the same direction, the locating protrusions of one battery module cannot fit into the indentations of the other battery. Therefore, battery modules can always be arranged adjacent each other such that the connecting terminals of opposite polarity are aligned alternately, whereby the risk of short-circuiting by joining connecting terminals of the same polarity is eliminated.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.